Crucible-furnace.



G. KEITH.

cuclBLE FunNAcE.

APPLIATION FILED OCT. 23. l9l5- 1,241,397, Y PatentedSept. 25, 1917.

4 SHEETS-.SHEET G. KEITH.-

CRUCIBLE FUHNACE. APPLICATIQN FILED ocT. 2a. 1916.l

Patenteu sept. 25, 1917.

4 SHEETS-SHEET 2'- G. KEITH.

cnucl'BLE fuRNAcE.

APPLICATION FILED OCT- 23. Iv9l6.

4 SHEETS-SH E 3.

1241-5397. I ratemdsept. y917.

l V671 "L /f l G. KElTH.

'CRUCIBLE FUHNACE.

APPLICATION FILED OCT- 23, 1916. l

Patented Sept. 25, 1917,

4 SHEETS-SHEET 4- Y 'GEORGE KEITH, 0F- LONDON, ENGLAND, ASSIGNOR OF ONE-HALF TOf JAMES KEITH, OF v LONDON, ENGLAND. l

' CRUCIBLETFUBNAGE.

To all whom t may concern.'

Furnaces, of which Be itv known that I, GEORGE Knrriaua 'subject of the King of the United Kingdom ofv Great Britain and Ireland, and residing at London, England, have invented Va certain ynew and useful Improvement in Cruciblethe following is a specification. Y

o This invention' relates to improvements in 5 crucible furnaces. l

In the 'use of crucible furnaces fired from which the crucible is'composed, the crucible Y deteriorating rapidly in consequence ofthe flaking 0E of large pieces from the lower end onwhich the name first iinpinges.

Again, in the operation of existing gasfired crucible furnaces', particularly when `large-,crucibles are being dealt with', there is @encountered thexdrawback that the provi' sion of sufficient spacearound the crucible to permit-the crucible tongs to grip the cruciblesecurely and low enough downv in volves material reduction of the efficiency -of-thefurnace from the point of view of f the space between the top of the crucible Y consumption of gas.

f the mixture tangentiallyand with a slight In a crucible furnace according to the invention provision fis* made for introducing *upward inclination into a recess which may material,- the products of combustion being.y reflected downwardly by the cover and led j i downward between the crucible and the inybe-formedl in the 'cover of thefurnace', such :cover being composed 'of' highly refractory terior wall o f the furnace-which wall preferably conformsl to the contour of the cruciblewhile being spaced therefrom 'sufficiently f to leave a practicable working space forv the downward passage-'ofthe hot products. v

Due to this4 inversion ofthe usual firingv operatiom-'the Yrefractory-top cover` of the ivfurnacel receives the first shock ofthe' in-r coming jets, the action being in the-nature ywhen the Acontents of the crucible are heated from below in theusual'manner the metalin the bottom of the crucible is melted.L andy lbecomes thoroughly hot long before the specification of Letters raient. Patented Sept. 25, 1917.

" Application filed. October 2k3; 1916. ySeralNo.127,176.

^ metal floating on the top does, while the addition of solid metal to the molten or partially molten contents of the crucible has a chilling effect andI even tends to cause solidi-fication ofalready molten metal, when the contents of the crucible lare heated from above the result is to improve the circulation, the metal 'flowing tothe bottom as it becomes molten and heavier--it being understood that m'ostfof the metals treated vin crucible furnacesl contract on liquefaction.

`In addition, the heating of the crucible by the hot currents passing down the side of =the same is distributed over the surface of the crucible, there being, in general, no

A'excessive local actionthe -severest-action being at'the -upper edge which is exposed `to the highest heat but which, unlike the bottom, can be allowed to become considerably worn before the crucible is rendered entirely useless.

"To provide --for accommodation of the tongs I arrange for effecting relative vertical displacement of the crucible and the inner wall of the furnace.

I prefer toprovide for vertical displacement of the crucible-supporting pedestal,

thus permitting reduction to a minimum of 'and `the'top of the furnace, while leaving it possiblev to heap unmelted ingots on the top ofthe crucible when it is first introduced into the furnace; it being understood that reduction of the internal vdimensions of the furnace entails the attainmentof a ,higher temperature for a given consumption of gas, and therefore of increased efficiency.

Alternatively,the inner wall of the furnace may be formed as a separate liner, be-

tweenwhich and a crucible-supporting pedestal at the bottom is an` annular space for the escape of combustion products, provision bewing made for lowering the liner temporarily vto the base of the furnace so as to leave a substantial clear annular space raround the- Lcrucible, sulicient to permit convenient adjustment of the tongs. v l

To provide for preheating ofithe mixture there is fitted yin the vfurnace a pipe or passage through which themixture on its way to the nozzles may be led, such passage being locatedkin a high temperature zone so that the mixture passing therethrough may be .highly heated. To protect the nozzles from injury due to excessive local heat, they y nace casing proper, such annulus beingrxf.

,are desirably thermally connected with an annulus forming the upper part 'ftlie' 'fur-Y posed to the atmosphere and serving lto diss sipate excessive heat.

To'insure more even distribution 'of the kheating action, the nozzles may be supplied with mixture lfromanvannulus coaxial with the Crucible and thermally Vconnected with the upper part of the furnace casing proper,

v V the cross-sectional area of the annulus ditive'construction yof lid. Figs. 5 and AGrepresent in vertical section'and transverse secfb'lefis vertically movable. Fig. v2` is aside elevation. Fig. 3 is a part sectional plan,

Ishowing the lid swung into open position..

Fig. k4 is a detail View .showing an `alternation analternative arrangement of the noz-l zles. y 4

Referring to Figs. 1, 2 v,and 3, denotes a T-shaped casting, the head of whichk extends to opposite sides lof the base of `thestruC- ture,-and works in vertical channels.

'the ends of the castingare attached chains 2, each of which passesovera; pulley 3 fixed on the top of the base,and thence to another vpulley 4 fixed ona crossshaft 5.

The :ends of the` chains are attached to the pulleys4, the diameters of which are -such that less .than one complete revolution-will .give the necessary lift to the pedestal. The

cross shaft 5 is revolved means of a worm wheel Tand worml 8. The shaft of the latter may be carried upward to any4 convenient position for.` working'. It will be seen that the chains 2 will lift the casting 1 bodily, and maintain it level in one plane.

The mixture of gas and air is vintroduced by way of the pipe connection 11- passing into the base, where the mixture is heated by the waste products.` 'f lhe'- pipe 11 branches into two .vertical pipes- 12 which V'pass `through the uptake or chimney, the

preheating of the mixture lbeing thus continued luntil the mixture is almost `about to enter theznozzles. To thel branches .12 `'are connected the nozzles 13 and 14 which are vin goodV thermal connection with, and are preferably cast in one'piece with the' annulus .l5-constituting, as it were, a `flange on 'the upperend oflthe furnacecasing and serving to dissipate excess heat so -that the y-tempe'i'aimre of the nozzles may be main tained within lpractical vlimits, having re- 1 gard -to the circumstance that a highly .pre-

heatedmixture is employed, andi/that the rsurroundings are at a high temperature. The

nozzles 413 and 14are arranged' substantially tangentially, with respect to the crucible, and-at a slight upward inclination, whereby the products of combustion are reflect- `ed downwardly by the cover 17 into the space between the crucible and the .interior wall of the furnace. A sand receiving groove 16 formed in the annulus 15 serves as a lute for effecting a tight closure of the furnace cover 17 which is shown fitted with a collar 18 arranged to .dip -into the lute. The cover 17 is arranged to tilt upward to swing clear of the lute yand the top of the `furnace in a manner which will best be understood from consideration of Figs;- 1 and 3. As shown,

the frame of the cover 17 is attached loosely by means of abolt 19 `to a casting 20, which' is hinged at 21 to a casting `22 rotatable aroundv the -iixed spindle 22X-, For tilting the cover 17 there are provided -t'he cam 23and the lever 24. It will be seen ythat-whenthe lever 2,4 is-moved intofhorizontal position c shown in dotted lines, the cover 17 will vbe tilted upward yinto a lposition such that it "can be conveniently swung in v'horizontal direction by actuationof the. lever 24. The arrangement isy suchthat in the raised posi- `tion of the 'cover the bolt19 is in tension,

and the -lower part of the cover bears on 'the extensions 25 formed onthecasting k20.

YIt will jbe seen accordinglyithat when .the

fractory materialof the cover can berepaired or renewed conveniently.

In the form shownin Fig. 4vthe `cover 17 is formed with a recess constituting a chamber into which the burner mixture from the 'nozzles is introduced. The cover 17l is also shown as provided with alsight hole 26 having a cover yor lid 27 fittedfwithaconnection 28 by means of which gas, can be introduced to the top Vof the crucible, preferably when the-glatter is raised -so as to touch ythe cover 17, Vfor the purpose of reducingor preventing oxidation ofthe.v ymaterial being melted.

' In Figs. '1 lto 4 are shown-,arrangements employing only a pair of nozzles: adapted to direct .the mixture tangentially It will v be understood, however, -thatlany .convenient niunber of nozzles maybe employed. Y

. In Figs. 5 `and 6 isA represented an advantageous arrangement in which the .nozzles -32 .are arranged Jin a circular row and `in communication with a hollow ,annulus 31 into which openstheupper end of the Apipe 12X supplying the mixture. The annulus 31 is flanged and extends over the upper vpart of the furnace proper, the'cavity in the interior of said annulus being of lgradually diminishing cross-sectional area.

vvcover is swung open it can easily be reversed byrevolving it on the bolt 19, sodthat the -re#` It will be understoodrthat the invention `.130

' and with a slight upward inclination 'into' naines? is not limited to the details of construction above described. For example, means other than herein shown may be provided for effecting relative vertical movement` of the liner and Crucible, and other preheating arrangements may be adopted.

What I Claim is l. In Combination, a gas-fired Crucible furnace presenting a recess adjacent to the upperv end thereof and constituting an initial combustion chamber, and means for introducing` combustible mixture tangentially and with a slight upward inclination intol said recess and for reflecting downward the heat and combustion products.

2. In combination, a gas-fired Crucible furnace having a liner, said furnace presenting` a recess adjacent to the upper end thereof and constituting an initial combustion chamber, means for introducing combustible mixture tangentially and with a slight upward inclination into said recess and for reflecting downward the heat and combustion products, a Crucible within said furnace, and means for effecting relative vertical movements of said Crucible and liner.

3. In combination, a gas-fired Crucible furnace presenting a recess adjacent to the upper end thereofk and constituting an initial combustion chamber, means for introducing combustible mixture tangentially said recess and for reflecting downward the heat and combustion products and a pipe for leading the mixture to the upper end 0f the furnace, said pipe so arranged as to permit preheating of the mixture on its passage upward.

.4. In combination, a gas-fired crucible furnace casing having its upper part exposed to the atmosphere and presenting a recess adjacent to the upper end thereof, and upwardly directed nozzles for introducing combustible mixture tangentially and with a slight upward inclination into said recess, said nozzles thermally connected to the upper part of said casing.

5. In combination, a gas-ired Crucible furnace casing having its upper part exposed to the atmosphere, a hollow annulus of tapering cross section, said annulus thermallyl connected with the upper part of said casing, and a series of tangentially and upwardly directed nozzles arranged in a circular row, said nozzles being in communication with said annulus.

6. In combination, a Crucible furnace casing, a cover for said casing, a vertical spindle fitted to said casing, a casting revoluble around said spindle, a second casting hinged to said iirst-mentioned casting, the axis of the hinge being horizontal, a horizontal bolt disposed diametrically vof said cover and connecting said cover to said second casting and permitting movement of said cover around the axis of said bolt, and a lever pivoted to said second mentioned casting and formed with a cam surface engaging said first-mentioned casting, said lever and cam serving to impart tilting and horizontal movements to said cover.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

GEORGE KEITH.

Witnesses:

WALLACE CRANs'roN FAIRWEATHER, HENRY MASON.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, ID. C. 

